Figure 6. Business category and data flow of power dispatching
In addition to control area and non-control area services, there is management information zone for organization and management of production and personnel. More services such as administrative telephone network management, electric power enterprise data transmission are also involved in such zone. These services of management information zone are carried on enterprise data network.
3.2. Challenges of Electric Power Data Transmission
During the operation of power grid, the operating information of power plant/station such as voltage, current, active power, reactive power, circuit breaker opening/closing status is collected through various sensors installed on primary equipment like lines, buses, circuit breakers, transformers, generators, etc. Such information is used for emergency control by local control devices such as relay protection and safety automatic devices, and is also sent to dispatch master station through dispatch data network channel.
The transmission of electric power data from a plant/station to dispatch master station occurs in three ways: (1)some measurement data are regularly sent to master station in real-time; (2) alarm information and fault analysis results are sent directly after generation; (3)when the master station summons monitoring signals and/or graphical model information, the plant/station send data immediately. These data transmission methods can be summarized as follows: when there is no special data demand, data from plant/station are send to dispatch master station periodically; when any plant/station or dispatch master station triggers a data transmission event, such as the emergence of alarm information in plant/station or data summon request from dispatch master station, the plant/station would immediately send corresponding data to the master station.
These data transmission methods are adopted because power grid has high requirements on data transmission time delay performance. As a bridge connecting power plants and load demands, any change in load side may cause fluctuations in entire power grid’s operating status. Various protection devices and automatic control equipment are used to enhance the local stability of power grid. And in order to maintain the safe and stable operation of power network, real-time monitoring of whole network status by dispatch control center is necessary. Currently, power grid lacks technical methods to judge the credibility of electric power data and mainly relies on traditional hardware such as firewalls and encryption isolation devices to guard against malicious attacks and data tampering. As energy infrastructure, power grid security defense level urgently needs to be further improved.
Applying blockchain technology to the field of electric power data transmission will bring three advantages: first, it effectively enhances the credibility of electric power data, laying foundation for the future intelligent and digital development of power grid; second, it can establish a reliable data traceability mechanism, providing a basis for the analysis and judgment of various events; third, it would optimize current power data organization, supporting data governance and management for power enterprises.
4. Electric Power Data Transmission Based on Parallel Proof of Work Algorithm
Although blockchain technology can effectively enhance data credibility and traceability, the drawbacks of current consensus algorithms restrict their applications in electric power data transmission.
This paper proposes a Parallel Proof of Work algorithm (P-PoW) based on early blockchain consensus mechanism, for the sake of enhancing the credibility and traceability of electric power data transmission.
4.1. Principle of Parallel Proof of Work Algorithm
The core idea of Parallel Proof of Work algorithm is to separate Proof of Work calculation process from new block generation process. Figure 7 shows the schematic diagram of Parallel Proof of Work algorithm principle. The blockchain structure shown is similar to Figure 1, where each block is divided into a block header and block data area. For P-PoW algorithm, block header contains P , which is a hash pointer to previous block header. M stands for the Merkle root hash of current block data. TS represents the timestamp at which moment current block is generated. And S is the signature of P-PoW algorithm. The subscript indices in Fig. 7 representing current block order. In block data area, D is the electric power data written into block, with two subscripts representing the position of data item in block data area and the current block order, respectively.
Unlike PoW algorithm, P-PoW algorithm no longer iteratively calculates block header to find a suitable random number nonce to generate a new block. Instead, P-PoW algorithm extracts the hash pointer Pfrom block header and generates a signature S by iteratively executing P-PoW algorithm. At the same time, to achieve real-time transmission of electric power data, P-PoW algorithm has eliminated the block generation target field in block header.